Apex domains cannot have CNAME records.
Question and response
Question
dig elastic-ssl.ui-r.com. NS
Answer
elastic-ssl.ui-r.com. 5 NS ns-1and1.ui-dns.biz.
elastic-ssl.ui-r.com. 5 NS ns-1and1.ui-dns.de.
elastic-ssl.ui-r.com. 5 NS ns-1and1.ui-dns.org.
elastic-ssl.ui-r.com. 5 NS ns-1and1.ui-dns.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0